Printing element and method of making same



May 26, 1936..

ffy M MM@ Patented May 2s, 193s UNITED 4STATES PATENT oFFicE GSAMEWilliam C. Huebner, Chicago, Ill. Application July 12, 1932, Serial No.622,051 5 claims. v(el. i1-415) This invention relates to improvementsin printing element and method of making same.

One object of my invention is to provide a printing element such ascommonly termed a press plate, which will possess longer life than thoseheretofore known and whereby longer editions may be printed therefrom atless cost.

Another object of my invention is to provide a printing element of thecharacter indicated in the preceding paragraph, which will have aprinting surface composed of ink-receptive or retaining portions andink-repellent portions and wherein the ink retaining portions are bondedto the metal sheet in a more tenacious and permanent manner than inpress plates heretofore employed.

A further object of the invention is to provide a printing element inthe form of a photographically prepared press plate, wherein theinkreceptive or retaining portions or areas of the surface,corresponding to the image to be printed, have an oxidized union or bondwith the metal and the ink-repellent portions vor areas. of the surfaceare on non-oxidized portions of the metal.

Another object of my invention is to provide an improved process ormethod for preparing printing elements of the character indicated in thepreceding paragraphs, the improved method or process insuring true,clear and sharp impressions.

Other objects of the invention will more clearly appear from thedescription and claims herein'- after following.

In the drawing forming a part of this specification, Figures l to 7 aremore or less diagrammatic sectional views of portions of a printingplate illustrating several of the successive steps of the process ofpreparingvthe same, it being understood that the thicknesses are greatlyexaggerated in order to better illustrate the invention. And Figure 8 isa cross sectional view of a portion of a. special form of plateembodyingtwo outer layers of metal and an interposed resilient layer.

In carrying out my invention, a metal plate or sheet I0 of thedesired'size is first obtained,

said sheet or plate being of any suitable metal such as steel, zinc,aluminum, copper and/or alloys. The metal plate may be either polishedor with a very fine grain on the surface thereof and is thoroughlycleaned to remove any possible grease or other foreign matter. To cleanthe metal sheet, the same is preferably treated with a cleaning solutioncomposed of one ounce of caustic potash to one gallon of water, followedby a solution of oneand one-half ounces of yhydrochloric acid to agallon of water, the surfacefof the sheet being scrubbed, as with abrush, and thereafter rinsed clean with water. In this cleaning, theacid solution is used to neutralize the caustic solution.

' After thorough cleaning and rinsing and while still wet, alight-sensitive layer, film 'or coating I I is applied of any desiredcomposition7 dependent upon different requirements, one such coating orl0 solution which I have found satisfactory being made up as follows. Asolution of glue and water in the, proportions of six ounces of glue totwelve ounces of water is iirst combined with another solution comprisedof water and flake albumen in the proportions of twelve ounces of waterand two ounces of flake albumen. To the two solutions just described,after being thoroughly stirred and mixed, is added a third solutioncomprised of one and one-quarter ounces of ammonia dichromate and twelveounces of water. This final solution, after being filtered, ispreferably applied to the surface of the'metal sheet by placing thesheet in what is commonly known as a whirler4 and flooding the solutionthereover while the sheet is being rotated. The sensitized coating orfilm is then permitted to set and dry thoroughly and is then ready for aphotographic exposure.

A photographic printing ,plate or film of the image, design or subjectmatter to be printed, and whereon the image, design or subject matter isopaque, that is, the reverse of the usual negative, is made. With thisphotographic printing plate or lm, an exposure is made on the sensitizedpress plate While the two elements are in intimatel and uniform contact.The light acting on the sensitized layer or coating of the press plate,hardens those portions of the sensitized lm, rendering said portionsinsoluble in water, as will be understood, and leaving those portions ofthe light-sensitive film corresponding to the image, design or subjectmatter, soft and soluble in water. Such exposure, depending upon thecharacteristics of the light-sensitive film or coating and the intensityof the light source employed, may be from approximately eighteen secondsto one minute. I

After the press plate has thus been subjected to the light action, thepress plate is .treated first by iiooding the entire plate with waterand then with running water, preferably in a trough, to remove thoseportions of the light-sensitive film which were not acted upon by the'light and which correspond to the image,`design or subject matter to beprinted and as indicated by the spaces or gaps I2-I2 in Flgure 1. Forsimplification in the description and claims, the term image will be usehereinafter to include any picture, design, writte matter yand/or anyother subject matter which it may be desired to have printed.

After the press plate has been thoroughly washed after exposure, it isthen given a bath in an ammonia solution preferably consisting of oneounce of ammonia to one gallon -of water, thus rendering thoselight-hardened, Yexposed portions of the illm on the press plate,receptive to a dye solution. y

After the ammonia bath, a dye solution is flowed over the plate, suchdye solutiony being of suitable color and composition, one such solutionwhich I have found satisfactory consisting of one quart of water and oneounce of dye such as methyl violet. The dye solution adheres to theretained, light hardened or non-image portions I I of the film surfaceon the press plate, thus setting off and rendering clearly visible theclean portions o r areas I2 (non-dyed) of the press plate surfacecorresponding to the desired image. l

The entire surface of the press plate is now gone over with a solutionpreferably consisting of one gallon of water, and two Aounces ofbicarbonate of soda. The application of this solution, which ispreferably applied with a cotton wad soaked in the solution, furthercleans the plate, removing any glue or thev like from the finer portionsof the image areas which were not removed by the original water washing.The press plate now is in a condition where all details of the image tobe printed, are represented by the thoroughly cleaned metal surface ofthe press plate and which Were originally protected from the lightaction by the opaque areas of the printing plate or llm corresponding tothe desired image.

The press plate, afterthe application of the dye solution and cleaning,as above mentioned, is then dried as quickly as possible by blotting thesurface with news print paper and drying with an air blast. Whenthoroughly dry, any areas or portions of the press plate which are notto carry any printing (such as margins or borders) may be stopped outwith a thickened sensitized solution similar to thatinitially used insensitizing the plate or sheet but wherein the glue content ispreferably increased approximately 100%. The thicker glue sensitizingsolution is applied in this instance, preferably by brush, on suchportion or area (as for instance the borders or margins) where printingis not desired. When the light-sensitive solution is set and dried, theplate is again exposed generally to light action, thus hardening thelast applied light-sensitive solution which is thus rendered insolublein water.

The plate is now in a position to be intaglio etched, then oxidized, andhave the ink receptive compound bonded thereon. To accomplish this thefollowing procedure is employed.

'I'he image or bare metal areas of the plate are now intaglio etched asindicated at I3-I 3 in Figure 2 and a satisfactory solution therefor ismade up of eight ounces of perchloride of iron at 47 Baum mixedthoroughly with a half ounce of nitric acid. This solution or mixturemust be applied immediately after mixing, winch is done by spreading thesolution over the plate uniformly as by means of a rubber set camel hairbrush or by floating over the plate with suitable apparatus designedtherefor. The etching solution is allowed to act on the image areas tofthe-plate for a short time, say twenty to thirty seconds, whereupon theplate is immediately blotted with a large sheet of blotting paper and/orflooded with bicarbonated water solution'and thoroughly rinsed to removethe etching solution as quickly as poslsible. The plate is then drainedand blotted with clean news print paper and dried quickly by air blast,care being taken to make the drying complete. Upon completion of thedrying, the plate is next hand wiped thoroughly with a soft cloth ball.'

preferably cheesecloth, to remove any loose, dry iron oxidized particlesthat may cling to the image areasof the plate or the plate can be wipedwithany suitable solvent such as acetone, alcohol, etc.

The next and extremely important step of the process is the oxidizationof the image areas' just etched and the application and bonding orunionization thereto of the ink-receptive compound. The latter, whilecapable of considerable variation, depending upon conditions such as thecharacter of inks subsequently to be employed in printing, mustnevertheless embody several necessary qualities. First, theink-receptive compound must be such that, after oxidization andapplication of the oxidized bonding compounds to the plate, lt will beable to resist without deterioration, the caustic potash and/or acidsolutions subsequently employed on the plate to remove the non-image farea portions of the sensitized film, as hereinafter explained.Secondly, the compound must be perfectly receptive to the greasy ink forsubsequent printing in the press and, finally, the compound must be suchas to eifectuate oxidization of the etched or image areas of the platewhile effectuating a bond or union of the greasy ingredients of thecompound with the oxidized metal in order to obtain a permanent,tenacious grip or union that will insure long printing life of the platein the printing press.

To obtain the above indicated desired results, any solution or mixturewhich liberates oxygen freely when drying slowly in the intaglio etchedimage areas I3 is applied to produce a grease receptive oxide. One suchsolution or mixture found satisfactory in the average situationcomprises a solution of potassium chlorate and water in the proportionsof one sixteenth ounce to thirty-two ounces respectively, which ispreferably applied by flowing the same over the surface of the plateimmediately followed by owing an acid solution within the intaglio imageareas of the plate as indicated by the dash lines I4 in Figure 3, andthe oxide thus formed constitutes what may be termed the first formedlayer of an oxidized bond between the base metal of the plate and thenal complete y ink-receptive coating on the image areas.

After the plate is dried, anoxidizing bonding solution or mixture isapplied. Such solution or mixture should comprise any greasy substanceor compound which will unite with the oxidized areas above referred toand which will dry and oxidize to a degree sufficient to resist causticpotash solution or acid solutions and which will also produce asatisfactory base that will be ink-receptive when the platel is inked upin the printing press. Such an oxidizing solution or mixture foundsatisfactory may be composed of a mixture of tar oil or oils derivedfrom coal tar bases which are mixed `with oxidizing agents such as redlead, litharge,

manganese dioxide, manganese borate o r other similar well knownoxidizers used in printing inks, A satis actory mixture may consist of:

Ounces Red lead $41 Coal tar creosote 1 Coal tar oil $4; Carbolic acidnl,

A suitable tar oil in the immediately preceding formula is Long F Pitch.'I'his compound is preferably applied by rubbing the same into saidpreviously oxidized image areas on the plate and then allowed to dry,thus completing what may be termed the nal oxidized bonded coating overthe image areas as indicated at [6in Figure 5.

A coating of asphaltum is then rubbed on the plate over which in turn isapplied a coating composed of parailin wax and paraflin oil and which isrubbed down smooth. These coatings obviously provide a protective mediato resist the caustic potash solution subsequently employed, ashereinafter described. The image reproducing areas of the plate are nowprovided with an ink-receptive and water and acid repellent compoundtenaciously and permanently bonded or intimately coaies'ced with andunited to the base metal of the plate.

The plate is next flooded with a caustic potash solution, preferablyconsisting of one gallon of water, one ounce of caustic potash and oneounce of ammonia. This solution is spread by means of a suitable brushover the entire surface of the plate until the light-hardened ornon-image areas of the sensitized lm become soft, whereupon the plate isscrubbed as with a soft brush, then iiushed with running water to removeany remaining caustic potash solution and most of the softenedsensitized film. The complete removal of the light-hardened or non-imagearea portions of the sensitized lm is effected by iiooding the platewith a solution consisting, preferably, of one gallon of water and oneounce of hydrochloric acid and during which the plate is again brushedover with a suitable brush or with a wad of heavy liannel to remove thefiner traces of the light-hardened portions of the sensitized film. Thepress plate is then in the condition where the image areas I6 thereonwith the ink-receptive coating or compound stand out in clear and sharpcontrast and relief from the remaining non-image portions or .areas ofthe plate as shown in Figure 6, which are clean and free of any coatingor film.

The press plate is next treated with any suitable desensitizing etch,such as satisfactory etch consisting of one half ounce of phosphoricacid and thirty-two (32) ounces of gum arabic solution, testingapproximately forty per cent (40%) on a water hydrometer. A

After the application of the desensitizing etch. the plate is washedwith running water and thereafter preferably gummed up and rubbeddownsmooth and fanned dry, with the plate having a ush coating comprised ofimage ink-receptive areas I 8 and non-image, ink-repellant areas, I1, asillustrated in Figure '1.

The plate is now ready to be run in the press. If, as for instance inchanging from the use of a ldark to a light colored ink, the resists areremoved from the image areas by suitable solvents, nevertheless theimage areas retain the oxides formed therein and chemically bonded tothe base metal and are still receptive to-all greasy inks and willcontinue to print becau of the tenacious grease receptive bond with thebase metal, a result never heretofore obtained so far as I am aware.

In the preceding decription, I have set forth with particularity varioussolutions, mixtures and compounds and a detailed sequence of stepsemployed in connection therewith which I have found extremelysatisfactory in actual practice under average conditions. As will beobvious to those skilled in the art, a wide range of variations ispermissible both as to the actual ingredients used and percentages ofingredients entering into said solution, coatings and mixtures without,however, departing fromthe essential features of the invention, suchvariations referred to sometimes being found desirable on account may beemployed and different metals of which the press plate may be composed.

In certain instances requiring especially` fine work, it is desirable tostart with a press plate having a smooth polish iinish in order that theetching of the image areas may be absolutely uniform while at the sametime it may be advantageous to have the non-image areas of the platewhen ready for the press, roughened or grained. This may be accomplishedin carrying out my invention by roughening or graining the non-imageareas of the plate after the reversing of the image areas has beencompleted. by subjecting said nonimage areas of the plate to a suitableacid and a basic salt, depending upon the base metal in the press plate.I am aware also that the oxidized bonded image areas on the press platemay be obtained without deep etching said image areas, the oxidizedimage areas being formed on the original surface of the press plateafter the image areas of th'e light-sensitive film have been removed'and without etching. It is also possible to etch the image areas of theplate to produce the intaglio effect, when desired, by electrolyticaction on such image areas after the corresponding portions of thelight-'sensitive film have been removed and the non-image areas suitablyprotected against electrolytic action. Another variation is to producean oxidized image area intaglio eiect without actually intaglio etchingof the press plate metal, by electrolytic action as, for instance, byproducing the oxidized bonded image areas on the plain surface of thepress plate metal without etching and, after the reversing step,depositing metal on the non-image areas of the plate electrolyticallyimmediately after the drying of the plate and removal of the lighthardened portions of the light sensitive film. Various other changes andmodifications all within the purview of the inventionvwill be evident tothose skilled in the art.

In the preceding description, I have confined the same to thepreparation of the surface of a single sheet of metal used as a pressplate. The invention is equally applicable to both sides of a specialyieldable printing plate such as shown in ,Figure 8 wherein two thinsheets of metal 20`20 have interposed therebetween and united thereto,an intermediate layer o f rubber 2l. In this special form ofpress plate,the metal sheets, grained or polished, may be about /.1000 of an inch orless in thickness and the intermediate rubber layer about al, of aninch. Such a specially formed press plate possesses numerous advantagesin that, on account of the thinness of the outer metal plates or sheetswith the rubber backing the prepared printing surface will yield as muchas may be necessary to compensate for irregularities or variations inthe-paper being the preferred manner of carrying out my invention, butthe sameis merely illustrative and I" contemplate all changes andmodifications that come within the scope of the claims appended hereto.

I claim:

1. The herein described method of preparing a press plate whichincludes: removing the image areas of an exposed sensitized lm coatingfrom the surface of a metal plate; intaglio etching said image areas;oxidizing said image areas; applying an oxidizing mixture to the thenoxidized image areas; and applying to said image areas an oxidizing,ink-receptive compound. l

2. In the method of producing an ink printing element having a metalbase, the improvement which includes: applying to predetermined imageareas of the surface of Ithe metal plate, an oxidizing agent and by thechemical action between said agent and metal plate, creating'agreasereceptive oxide, in situ, in said image areas; applying to saidgrease-receptive oxidized image areas, a greasy, oxidizable compoundcontaining an; oxidizing agent and by the` chemical action thereofuniting, in situ, the compound with said Qan oxidizing agent and, by theresulting chemical action, creating a grease-receptive oxide, in

oxidized image areas by further oxidization; and then applying to saidimage areas an oxidizable ink-receptive mixture containing an oxidizingagent and by chemical action thereof uniting the mixture, in situ, withthe previously formed 5 oxides. l

3. In the method of producing an ink printing element having a metalbase plate, the improvement which includes: etching predetermined imageareas of the surface of the metal 10 plate and thoroughly removing-alloxides produced by the etching; then applying an oxidizing agent to saidcleaned, etched image areas and by the-resultant chemical actionproducing a grease receptive oxide, in`situ, in said image areas i thenl5 applying to said grease receptive oxidized image areas, a greasy,oxidizable compound containingan oxidizing agent and, by the resultantchemical action, uniting, in situ, said compound with the previouslyformed oxides; .and finally apply- 'ing to the oxidized areas, anoxidizable inkreceptive mixture containing an oxidizing agent and, bythe resulting chemical action, uniting the mixture, in situ, with thepreviously formed oxides.

4. In the method of producing an ink printing' element havinga metalbase plate, the improvement which includes: applying to predeterminedimage areas of the surface of the metal plate,

situ, in said image areas; and thereafter applying to thegrease-receptive oxidized image areas, oxidizable, greasy andink-receptive substances containing oxidizing agents and, by theresulting chemical reactions, uniting said substances, in situ, withsaid ilrst mentioned grease receptive oxide formed by said oxidizingagent.

5. A printing element-including a metal base plate and the surface 'ofwhich is provided with '40 a coating comprised of both ink-'retainingand ink-repelling portions, these portions of the plate corresponding tothe ink-retaining portions of the coating being oxidized and saidink-retaining portions of the coating including oxidized greasereceptiveand ink-receptive substances and in which the oxides are coalesced withthe metal oxide of the base plate.

' c. HUEBNER. 50

